Heat Treatment Options for Crusher Wear Parts

Two castings can leave the same foundry with the same chemistry and behave quite differently in service, and the reason is almost always the furnace rather than the melting shop.

Heat treated crusher wear parts are produced by a sequence of heating, holding and cooling steps that set the balance between hardness and toughness in the final part.

Get that sequence right and a plate wears evenly for months, while a missed soak or a slow quench can cut service life in half without any visible defect at delivery.

This article sets out the main routes, the parameters that control them, and the paperwork a buyer should expect with a wear part heat treatment order.

1. Why Heat Treatment Decides the Life of Crusher Wear Parts

Casting gives a part its shape and its chemistry, and heat treatment gives it its working properties.

Three properties matter for crusher wear parts: resistance to abrasion, resistance to cracking, and the ability to work harden under repeated impact.

No single microstructure delivers all three at once, so every heat treatment route is a compromise that is chosen for the load the part will meet.

The compromise shows up in the field in two opposite ways.

A part that is hard and brittle resists sliding abrasion well but cracks when a lump of tramp metal enters the chamber.

A part that is soft and tough absorbs impact without cracking and then wears away quickly on an abrasive feed.

Deciding which failure costs more in a given circuit is the first step in specifying a treatment.

The table below relates the main routes to the parts that normally use them.

Shenyang Delonshine Technology Co Ltd runs these routes in house, which means the record of the furnace cycle travels with the part rather than being lost between suppliers. That record is what makes heat treated crusher wear parts traceable back to a furnace cycle.

2. Wear Part Heat Treatment: The Four Main Routes

Wear part heat treatment in a foundry serving mines and quarries usually covers four routes, and the choice follows the grade rather than the customer's preference.

Manganese grades are solution treated, alloy steels are quenched and tempered, low carbon steels are surface hardened, and heavy castings are stress relieved after rough machining.

A fifth route, hardfacing, is applied on top of a finished part and is treated here as a surface option rather than a bulk treatment.

The order of the stages is fixed in every case.

A part is heated at a controlled rate, held at temperature long enough for the change to complete through the section, and then cooled at a rate suited to the grade.

Heating too quickly cracks thin sections, holding too briefly leaves the core untreated, and cooling too slowly allows the structure to revert.

Each of those three failures produces a part that looks correct and measures soft or brittle at the first inspection.

3. Solution Treatment for Manganese Crusher Wear Parts

Manganese steel arrives from the mould in a brittle condition and becomes useful after solution treatment.

The part is heated to roughly 1,050 to 1,100 degrees Celsius, held for a period set by its thickest section, and then quenched in water.

A common working rule is one hour at temperature for every 25 millimetres of section, with a minimum of two hours for thin parts.

The water quench is the stage that most often goes wrong.

An operator who delays the transfer from furnace to quench tank lets the temperature drop below the useful range, and the austenitic structure begins to break down before the part reaches the water.

The result is a casting at roughly 250 HB instead of one at 180 to 220 HB in the soft condition, and it work hardens poorly for the rest of its life.

Hardness testing on the finished casting catches the problem when the supplier tests every heat.

Ultrasonic inspection adds confidence about internal soundness, and a solution treated part with internal shrinkage will crack under load whatever its surface hardness reads.

4. Quenching and Tempering for Treated Wear Parts

Alloy steel used as a wear part heat treatment route is austenitised at roughly 880 to 920 degrees Celsius and then cooled fast enough to avoid the soft transformation products.

Oil and polymer quenchants are common for these sections, because a water quench on a thick casting risks a crack at the corners.

Tempering follows immediately, at a temperature chosen for the hardness wanted, and the part is then air cooled.

The tempering temperature is the control lever on the hardness and toughness balance.

A temper around 200 to 250 degrees Celsius holds hardness in the 300 to 350 HB range and suits a part that meets abrasion without shock.

A temper around 550 to 650 degrees Celsius drops hardness to roughly 240 to 280 HB and raises impact energy several times over, which suits a gear or a hub that carries torque and occasional shock.

Delonshine Technology records both the quench medium and the tempering temperature for every heat, because those two figures explain most service failures that are later disputed. They also let a buyer compare heat treated crusher wear parts from two sources on equal terms.

5. Surface Hardened Crusher Plate Options

A surface hardened crusher plate carries a hard outer layer over a core that stays tough, which is the arrangement wanted wherever a part meets both abrasion and bending.

Carburising diffuses carbon into a low carbon steel at roughly 900 to 930 degrees Celsius and produces a case some 0.8 to 2.0 millimetres deep.

Induction hardening heats a local band of the surface in seconds and quenches it immediately, which suits a seat or a shaft journal rather than a whole plate.

Hardfacing deposits a wear resistant alloy on a finished surface by welding, and it is often used to rebuild a worn plate before the next campaign.

The case depth matters as much as the case hardness.

A case that is too thin collapses under a point load and lets the soft core deform underneath it.

A case that is too deep approaches a through hardened part and loses the toughness the design was built on.

A buyer specifying a surface hardened crusher plate should state the case depth and the core hardness together, because a hardness figure alone does not describe the part.

The table below compares the surface routes on depth, hardness and typical use.

6. Choosing Between Through Hardening and Surface Hardening

The decision between through hardening and surface hardening rests on where the load sits in the section.

A part that must resist wear across its whole volume is normally through hardened, because the surface route would leave soft material behind the case.

A part that bends as well as wears is better surface hardened, because the tough core stops a crack that forms at the surface from running through the section.

Section size is the second factor.

A thick casting cannot be quenched through its centre without a severe risk of cracking, so the hard zone is confined to the surface by design.

A thin part quenches evenly and gains little from a case, since the whole section hardens anyway.

A worked example makes the point.

A mill liner at 60 millimetres thick is normally through hardened and supplied at a hardness that applies across the section.

A crusher plate with a bolted edge is often supplied as a surface hardened crusher plate along that edge, because the edge meets the most abrasion while the body has to flex. Delonshine Technology quotes the two routes separately so the choice stays visible to the buyer.

7. Heat Treatment Control: Furnace, Soak and Record

Control of the furnace cycle is what separates a repeatable part from a lucky one.

A temperature recorder with a calibrated thermocouple, a written cycle for each grade, and a signed record for each batch are the three basic requirements.

Where those are missing, a customer has no way to prove that the hardness measured at delivery will still apply after a year on the shelf.

Soak time is the parameter most often shortened under production pressure.

Cutting soak time by a third saves hours in the furnace and can leave the centre of a heavy section untreated, which shows up much later as a part that wears unevenly across its face.

A written rule that ties soak time to measured section protects against the habit.

Shenyang Delonshine Technology keeps the cycle record with the heat number, so a customer who reports a wear problem can be given the actual furnace data for that part.

8. Reading a Certificate for Heat Treated Crusher Wear Parts

A delivery of heat treated crusher wear parts should arrive with a document that supports three claims.

The first is the chemistry of the heat, reported against the grade specification.

The second is the treatment cycle, giving the austenitising temperature, the soak time and the cooling medium.

The third is the result of the hardness check, with the positions of the test points recorded rather than a single figure for the whole part.

Two further items are worth asking for on large castings.

A dimensional report shows that the part matches the drawing within tolerance after treatment, because a quench can move a thin section by a millimetre or more.

An inspection record for internal soundness covers the risk that a sound casting was cracked during quenching.

A certificate that reports a single hardness number tells a buyer very little, because a part can read correctly at one point and be soft 40 millimetres away. A surface hardened crusher plate should also carry the case depth in the same document, since that figure cannot be recovered from a bulk hardness reading.

9. Frequently Asked Questions about Wear Part Heat Treatment

9.1 What hardness should heat treated crusher wear parts have?

There is no single figure, because the target follows the duty. Manganese parts are commonly supplied at roughly 180 to 220 HB in the soft condition and work harden in service to well above 350 HB at the worn surface. Quenched and tempered alloy parts usually sit between 240 and 350 HB depending on the temper, while a chrome alloy liner may reach 55 to 62 HRC. What matters is that the hardness figure matches the failure mode seen in the machine rather than being high for its own sake.

9.2 Can wear part heat treatment be repeated on a worn casting?

A part that has already worn through its working section cannot be brought back by re-heat treatment, because the missing metal is gone and the treatment changes structure rather than dimensions. What can be done is a rebuild by hardfacing followed by a controlled cool, which is common on large liners where replacement would mean a long outage. A used manganese part that has been re-austenitised can regain work hardening capacity, but the cost usually suits heavy castings alone.

9.3 When is a surface hardened crusher plate the right choice?

A surface hardened crusher plate suits a part that has to resist abrasion on one face while continuing to carry bending or shock through the section. Typical examples are a plate edge that meets the feed, a shaft seat, and a wear pad that cannot be allowed to flex. Where the whole section is exposed to abrasive flow, through hardening gives a longer life for the same cost. The guide is whether the failure starts at the surface or inside the section.

9.4 How much does heat treatment add to the cost of a casting?

Heat treatment is normally a modest share of the delivered price of a casting, often in the range of 5 to 15 percent for a bulk route such as solution treatment or quench and temper. Surface routes cost more per unit area and are applied selectively. The saving from skipping treatment is real on the invoice and much larger in service, since an untreated part may wear twice as fast and take the replacement interval with it. For heat treated crusher wear parts the furnace is part of the product rather than an optional extra.